Sensor device and device for checking the operational condition of a harness of a safety seat

ABSTRACT

A device for controlling the correct operating state of a restraining harness, intended for a safety seat, including at least one retaining strap that is under tension when the harness is in the state of restraining the occupant, the device being intended to be disposed in a predefined area of the latter, the device including: at least one sensor device including an elongate flexible element that is suitable for being positioned on the strap, and in particular rigidly connected thereto in the predefined area, and that is provided with a measuring system to measure, in the predefined area, at least a level of bending and/or tilting of the strap, a device to collect values linked to the level of bending and/or tilting, and internal or external device configured to analyze the values and of communicating with a receiver for receiving information on the operating state of the retaining harness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of PCT/EP2016/052847, filed Feb. 10,2016, which in turn claims priority to French Patent Application No.15/00273, filed Feb. 12, 2015, French Patent Application No. 15/00274,filed Feb. 12, 2015 and French Patent Application No. 15/01824, filedSep. 3, 2015 the entire contents of all applications are incorporatedherein by reference in their entireties.

The present invention concerns a device for checking the correctoperational condition of a harness of a safety seat, in particular of achild's car seat, when an occupant is sitting in it. The presentinvention also concerns a sensor device for the implementation of such achecking device.

In the motor vehicle field various systems are known which enable it tobe checked that the devices intended to hold a child in a car seat usinga harness are being used correctly.

It will be noted that most harnesses intended to be fitted to children'scar seats include a first central strap, called a crotch strap, which isattached by one of its ends to the seat, and which passes between thelegs of the child, and ends at its other end with a locking buckle,intended to receive an end of two other straps, called retaining straps,which are positioned symmetrically relative to the seat, and which holdthe child in position on the seat, and then join up in the bottom of theseat with a strap, called a tension belt, the tension of which causesthat of the retaining straps.

Various systems are also known which, to check that a child is correctlyattached in their seat, check that the retaining straps are indeedengaged on closure, in the locking buckle. Such systems prove to beunable to check that the child is held correctly in the seat throughoutan entire journey, since they are not able to detect and signal amalfunction if, for example, one of the straps of the harness isreleased for one reason or another.

Systems are also known which can detect the presence of a child on aseat by means of a feeler positioned on the seat and which, furthermore,can check that the harness's locking buckle is correctly closed bymeasuring the angle formed by the crotch strap and the case of thelocking buckle. As with the previous one, such systems cannot detect allmalfunctions which result in a relaxation of the tension of theretaining straps in the course of use.

Systems are also known, through application WO 2007/115301, which checkthat the devices which hold a child in a car seat when the child is putinto it are being used correctly, by checking the pressure exerted bythe locking buckle against the seat. These devices are also unable todetect malfunctions relating to a lack of tension in the retainingstraps in the course of a journey.

Finally a device is known, through application WO 98/51545, formeasuring the tension of a retaining strap holding a passenger in a carseat which makes, use of a deflector device, which forces the strap tofollow a determined path such that, when the tension of the strapincreases the deflector device is displaced, and this displacement isdetected by a sensor.

It will also be observed that all the above-mentioned checking devicesrequire, to be installed in a specific car seat, that substantialmodifications are made to this seat beforehand, and they then requirethat new tests are conducted on the modified seat, these tests beingnecessary for it to be accepted by the official safety control bodies.

Another disadvantage, which is inherent to the various systems mentionedabove, is that none of them is able to communicate with the vehicle'snavigational control instruments.

The aim of the present invention is to propose a device allowingcontinuous checking, for the entire period during which an occupant, andin particular a child, is occupying a car seat, that this occupant isbeing held correctly, where this system can also be installed in asafety seat of any type, without requiring that specific adaptivemodifications are made to it. Additionally, if the occupant is no longerbeing held, or is being held incorrectly, the checking system accordingto the invention can transmit a warning, firstly to the vehicle'snavigational control instruments, and secondly to additional receiversystems which users are able to use, such as for example key fobs orsmartphones.

Another purpose of the present invention is a device for checking that asecuring harness, intended for a safety seat, in particular a child'sseat, including at least one retaining strap subjected to tension whenthe harness is in the state of holding an occupant, is in a correctoperational condition, where the said device is intended to be installedin a determined area of this strap, characterised by the fact that itincludes:

-   -   at least one sensor device including an elongated, flexible        element which can be positioned on the said strap, and in        particular can be securely connected to it, in the said        determined area, which has measuring means able to measure, in        this said determined area, at least one level of flexion and/or        inclination of the said strap,        -   means able to obtain values relating to this level of            flexion and/or inclination,        -   internal or external means able to analyse these values and            to communicate to receiver means data concerning the            operational condition of the said securing harness.

According to the invention, the retaining strap will be a shoulderstrap, and the said determined area will be close to a location where itis intended for the strap to be pressing against the shoulder of theoccupant.

The sensor device will preferentially be associated with an electroniccircuit, and the elongated, flexible element will be attached to it, inparticular as an extension to it, both of these elements being containedin a flexible, elastic envelope so as to form a module which can beimmobilised relative to the strap. One end of this device may includemeans able to attach it, in particular using a strap, to a headrest ofthe child seat.

The flexible envelope may have elasticity such that, when it is under nostress, it has an unbent shape. This elasticity may be at least partlycommunicated to it by an additional spring element, in particular onewhich is incorporated in its flexible envelope. This spring element mayconsist of at least one snap ring made of synthetic fibre.

The checking device according to the invention may include electronicmanagement means, particularly of the microcontroller type, containing aprogram to control the various associated sensors, and in particular aself-test program intended to be run on each new use of the child seat.

It may include means for remote communication with receiver means, inparticular of the Bluetooth type.

It may also include means able to take into account the physicalcharacteristics of the occupant, in particular of the child, and aboveall their size and/or their physical build.

Another purpose of the present invention is a sensor device intended toimplement a checking device according to the invention. This sensordevice may be incorporated in a retaining strap.

The said measuring means may also include at least one inclinationsensor, and at least one inclination sensor may consist of anaccelerometer.

In a preferred embodiment of the invention the sensor device willinclude two inclinometers installed roughly at the respective ends ofthe elongated, flexible element, where the difference between the twovalues delivered by these inclinometers gives a value of the retainingstrap's level of flexion. At least one additional inclinometer may beattached to them, which will preferentially be installed between thefirst ones.

In one embodiment of the invention the flexible element may include, atone end, a target in which one area becomes separated from a referencearea when it is subjected to flexion, and where measuring means areinstalled to measure the distance between the target and the saidreference area. The flexible element may be formed by an elongatedsleeve, the upper and lower walls of which will be kept apart byseparating elements, with the target installed in a portion of thesleeve distant from the strap. These measuring means can include a laserdiode device.

The measuring means can also include two electrodes installed on thetarget and in the reference area which constitute a capacitance with theair which separates them as a dielectric, and also means for measuringthe value of this capacitance.

The flexible, elongated element may also be covered with a coating, suchthat its electrical resistance varies when it is bent. This electricalresistor may consist of a coating containing embedded conductingparticles which, when it is appreciably rectilinear, will give it agiven resistance and, when it is curved, a resistance of another value.It may include means to measure the value of the said resistance.

Finally, the elongated, flexible element may include at least onecapacitive sensor.

Another object of the present invention is a safety seat, in particulara car seat, including a checking device and possibly a sensor device asdescribed above.

Ways of executing the present invention will be described below, asnon-restrictive examples, with reference to the appended illustration,in which:

FIG. 1 is a perspective view of a child's car seat which is fitted witha checking device according to the invention, represented before itssecuring harness is locked,

FIG. 2 represents a rear view of the car seat represented in FIG. 1,

FIG. 3 is a profile view of the car seat represented in FIGS. 1 and 2,

FIG. 4 is a view of the car seat represented in FIG. 3, in which a childhas been placed, but is not yet strapped in,

FIG. 5 is a view of the car seat represented in FIG. 4 after the strapshave been passed over the shoulders of the child,

FIG. 6 is a view of the car seat represented in FIG. 5 after the child'sretaining straps have been tightened,

FIGS. 7 and 9 are cross-section views of a first embodiment of a sensordevice belonging to a checking device according to the invention,respectively before and after flexion of the retaining strap on which itis positioned,

FIG. 8 is a top view of the sensor device represented in FIGS. 7 and 9,

FIGS. 10 and 12 are cross-section views of a second embodiment of asensor device belonging to a checking device according to the invention,respectively before and after flexion of the retaining strap on which itis positioned,

FIG. 11 is a top view of the sensor device represented in FIGS. 10 and12,

FIGS. 13 and 14 are schematic views of details showing a method ofmeasuring flexion by measuring a capacitance,

FIGS. 15 and 17 are cross-section views of a third embodiment of asensor device belonging to a checking device according to the invention,respectively before and after flexion of the retaining strap on which itis positioned,

FIG. 16 is a top view of the sensor device represented in FIGS. 15 and17,

FIG. 18 is a schematic view of an example of a flexion measurementprovided by the sensor device represented in FIGS. 15 to 17,

FIG. 19 is a view and a schematic of a variant embodiment of a sensordevice according to the invention,

FIG. 20 is a flow chart representing a first example of a method ofoperation of the present invention,

FIGS. 21a and 21b are partial top views of sensor devices usingcapacitive sensors,

FIG. 22 is a flow chart representing a second example of a method ofoperation of the present invention,

FIGS. 23a to 23c are schematic views showing the influence of thesetting of the seat headrest and of the size of the child on theinclination of the rear portion of the retaining strap.

FIGS. 1 to 6 represent a first embodiment of the present invention, inwhich a child's car seat 1 consists principally of a shell comprising abase 1 a, and a backrest 1 b. The shell has a harness which consistsmainly of a first central crotch strap 3 which is attached by one of itsends to base 1 a and which includes, at its other end, a locking buckle5, and two lateral retaining straps 7 and 9, which are positionedsymmetrically relative to the shell. The first ends of each of thesestraps 7, 9 are joined in a hook 11 which can work in tandem withadditional means of locking buckle 5, so that they can be locked in itin a position which immobilises a child in seat 1.

The other respective ends of these two straps 7 and 9 traverse apertures12 a, 12 b located in the upper portion of the shell, and then join oneanother on the reverse side of it in a connection device 13, to which atraction belt 15 is attached which traverses the shell and then emergesfrom it through blocking means 17.

In the present embodiment strap 7 has, in its upper portion, i.e. in anarea close to aperture 12 a through which it traverses backrest 1 b, acase 18, made of a flexible, deformable material, which containselectronic measuring means and also a sensor device 19 according to theinvention.

Case 18 can be attached to strap 7 by all means, and in particular bystapling, clipping, bonding, trapping, etc. It can also be incorporated,in particular during manufacture, in the strap. Case 18 canpreferentially be attached to an envelope surrounding the strap, wherethis envelope is held in place by a link close to the upper portion ofthe seat or of headrest 30 of the seat, as represented in FIGS. 23a to23 c.

As represented in FIGS. 7 to 9, case 18 contains an electronic circuit20 which is extended by a flexible tongue 23. The electronic circuit,which includes electric supply means, consisting for example of alithium battery 21, includes several sensors, namely a gyroscope 22, anaccelerometer 25 and an inclinometer 28. Operational management of thesevarious sensors, and that of sensor device 19, is performed by amicrocontroller 26 which has programming means able to implement thechecking device according to the invention.

Sensor device 19 which, inside case 18, extends electronic circuit 20,includes flexible tongue 23 which supports two accelerometers 24 a and24 b, which include, in a known manner, an inclinometer function whichwill be used in the present case. The two accelerometers arepreferentially installed roughly at the ends of flexible tongue 23, andare connected to microcontroller 26 by a wired link 27. As representedin FIGS. 7 and 9, each accelerometer measures its respective inclinationfo and fn relative to the same reference, and microcontroller 26 is ableto determine easily, using the difference of these two values, value fof the flexion adopted by flexible tongue 23, and therefore the flexionadopted by strap 7, i.e. f=fn−f0.

In a simplified embodiment of the present invention either aninclinometer or a sensor device may simply be used. It will beunderstood that the accuracy of the data available to the user will thenof course be lower, but it may prove of interest for simple, low-costembodiments.

As represented in FIG. 21a , it is also possible to use a thirdaccelerometer 24 c, which will be installed between accelerometers 24 aand 24 b. This accelerometer will enable microcontroller 26 to factorinto its management process the size of the child who is placed in theseat, as explained below.

A sensor device 19 using measuring means different from those describedabove could of course be used. Thus, in a second implementation of thepresent invention, which is represented in FIGS. 10 to 12, electroniccircuit 20 is extended by a sensor device 19 including a sheath 29 madeof a deformable, elastic material such as, for example, polyamide,polyether, polyester, isocyanate, etc. This sheath 29 is sufficientlyrigid that, when not subject to any stress, it can regain itsrectilinear shape, as represented in FIG. 10. Sheath 29 includes a lowerwall 29 a which is kept in contact with strap 7 and an upper wall 29 b.The inner face of lower wall 29 a receives spreaders 31, the function ofwhich is to keep lower wall 29 a and upper wall 29 b separated.

The sensor device has means enabling the existing distance between atarget 33, positioned at its end close to electronic circuit 20, and afixed portion of the latter, called the reference area, to be measured,as represented in FIGS. 10 to 12. These means consist, for example, of alaser diode 35 installed such that axis uu′ of its beam is roughlyperpendicular to target 33 when the sensor device is only slightlycurved. Laser diode 35 is connected to an interface connected tomicrocontroller 26 which can determine distance d between it and target33.

This being so, it will be understood that when a flexion force F1 isexerted on strap 7 sensor device 19, lower face 29 a of which issecurely connected to the latter, is deformed, as represented in FIG.12, and the separation between laser diode 35 and target 33 increasesand takes on a value of d′. Microcontroller 26, which receives thisinformation, is thus able to determine angular deformation f1, f2, . . .fn adopted by strap 7 during its deformation, and to deduce from thisthe flexion to which it is subject.

As represented in FIGS. 13 and 14, the means for measuring distance dcould also consist of two electrodes 38 which constitute, with the airseparating them as a dielectric, a capacitance the value of whichdepends on distance d separating them. Any flexion of strap 7 causes aflexion of sensor device 19 and the distance separating the twoelectrodes 38 increases and becomes equal to d′. The value of theexisting capacitance between the two electrodes 38 is sent tomicrocontroller 26 which can deduce from it the value of distance d′.Knowing new separation d′, microcontroller 26 can deduce from it theflexion adopted by strap 7.

Additionally, electronic circuit 20 contains communication means 40, inparticular of the Bluetooth type, which can transmit to externalreceivers, in particular such as devices of the smartphone type, orreceivers incorporated in the vehicle, and in particular to itsdashboard, the parameters collected or data output from the analysis ofthese parameters, which are managed by microcontroller 26. Thesereceiver devices may to this end have a specific application able tomanage the data transmitted by communication means 40.

Another type of sensor device could also be used, for example one suchas that represented in FIGS. 15 to 18.

As above, an electronic circuit 20, in particular of the type describedabove, is combined with a flexible, elastic strip 44, for example madeof a compound of polyamide, polyether, polyester, isocyanate, etc.However, this strip 44 is sufficiently rigid that, when not subject toany stress, it can regain its rectilinear shape, as represented in FIG.15. If necessary, of course, the stiffness of the flexible strip couldbe increased by combining it with a stiffer spring element made, forexample, either of a synthetic material or of metal.

As described above, the assembly consisting of electronic circuit 20 andof sensor device 19 could also be installed in a receiver unit, notrepresented in the illustration, consisting of a flexible, deformableand elastic material.

Strip 44 is given, over its entire length, a coating 46 made of aspecific polymer ink in which conducting particles are embedded whichgive it, when it is appreciably rectilinear, as represented in FIG. 15,a resistance of value R, and when it is bent, as represented in FIG. 17,a resistance of another value, in particular a higher value. Thus,according to the invention, one need merely measure the value ofresistance R of impression 46 in order to be able to determine thecurvature of strip 44, and therefore that of strap 7.

This measurement could be made by any other means and, in particular, asrepresented in FIG. 18, by means of a divider bridge 48 which can, in aknown manner, apply to an input 50 of microcontroller 26 a voltage vwhich depends on resistance R of coating 46, and therefore on theflexion of strap 7.

According to the invention, case 18 as described above, which is madefrom a flexible, deformable material, must also have an elasticity suchthat when it is not subject to any stress it returns to a positioncalled its “initial position”, which is preferentially close to anappreciably rectilinear position, as represented in FIGS. 7, 10 and 15.Case 18 will have such an elasticity due to its constituent materialand/or by being given spring elements, consisting in particular ofelastic snap rings made of a synthetic material, which willpreferentially be slipped on in appropriate longitudinal recesses madein the case.

An example of the operation of the invention will now be described. InFIG. 3, which represents seat 1 when empty, flexible case 18 containingsensor device 19, and consequently the reference axis of theinclinometer contained in it, forms relative to vertical yy′ an anglei0, and this value is transmitted to microcontroller 26, which thusknows the value of the inclination parameter

For its part, gyroscope 22 can detect any movement applied to seat 1, inparticular when the user places a child 2 in it, and can transmit tomicrocontroller 26 the value of a “jolt parameter” g.

The same applies to accelerometer 25 of electronic circuit 20, whichdetects any jolt applied to the seat relative to the vehicle, and anymovement of it in space, and which can transmit to microcontroller 26the value of acceleration parameter a.

In practical terms, and although in the present mode of implementationof the invention it is considered that the inclinometer consists of adevice distinct from the accelerometer, the latter can also be used tosupply inclination parameter i, as explained below.

For each condition detected during a period of operation which may be,in particular, of the order of 10 seconds, microcontroller 26establishes a table of values of the various sensors. Thus, in the idlecondition, i.e. before a child has been put into seat 1, we shall forexample have the following values:

Gyroscope 22: g=0

Accelerometer 25: a=0

Inclinometer 28: i=0

Sensor device 19: f=0

These various values are grouped by microcontroller 26 in a matrix thevalue of which will be represented by: [gaif], and it is communicated,via Bluetooth communication means 40, to the application contained in areceiver of the user which decodes it using an appropriate application,in particular a specific application in the case of a smartphone 56, anddeduces from it that there is no child in the seat. Such a process canalso of course be undertaken by microcontroller 26 itself.

When a child 2 is placed in seat 1, as represented in FIG. 4, gyroscope22 and accelerometer 25 detect the jolts caused by this action to placethe child in the seat, and the sensors' parameters then adopt thefollowing values:

Gyroscope 22: g=1

Accelerometer 25: a=0

Inclinometer 28: i0

Sensor device 19: f0

The matrix of values thus becomes [1000] and is obtained bymicrocontroller 26 and then communicated by the latter to the receiver,which deduces from it that a child has indeed been put into seat 1 andthat, since neither inclinometer 28 nor sensor device 19 have changedtheir values significantly, strap 7 has continued to be applied on theseat, and that consequently child 2 is not yet strapped in. Theapplication then displays on the smartphone a message similar to “Childin the seat”.

After this, as represented in FIG. 5, when strap 7 is passed over ashoulder of the child the values of inclinometer change and theparameters of the sensors then adopt the following values:

Gyroscope 22: g=1

Accelerometer 25: a=0

Inclinometer 28: i=1

Sensor device 19: f=0

The matrix of values then becomes equal to [1010] and is obtained bymicrocontroller 26 and communicated by it to the application. In thiscase the application observes, firstly, that an inclination has beendetected, which means that this is higher than it should be if strap 7were tight. The application also observes that a flexion has not beendetected (f=0), implying that the strap has not been tightened. Theapplication can consequently display, if desired, a message similar to:“Child not strapped in”.

When, as represented in FIG. 6, retaining strap 7 is correctlytightened, the value of the flexion changes and flexion parameter festablished by sensor device 19 becomes equal to 1. The sensors'parameters then adopt the following values:

Gyroscope 22: g=1

Accelerometer 25: a=0

Inclinometer 28: i=1

Sensor device 19: f=1

The matrix of values becomes equal to [1011] and is obtained bymicrocontroller 26 and communicated by it to the receiver. The latter'sapplication observes that, apart from the acceleration parameter, whichis still at 0 (meaning that the vehicle is stationary), all otherparameters are at 1, meaning that the child is correctly strapped in.The application will consequently display a message similar to “Childcorrectly strapped in”.

In a simplified embodiment of the invention one could also dispense withthe redundancy of the inclination and flexion parameters and, to do so,use only one inclinometer or only one sensor device 19 to determinewhether the child is correctly strapped in.

When the vehicle starts its movement is detected by accelerometer 25 andthe acceleration parameter changes to 1. The sensors' parameters thenadopt the following values:

Gyroscope 22: g=1

Accelerometer 25: a=1

Inclinometer 28: i=1

Sensor device 19: f=1

The matrix of values becomes equal to [1111] and is obtained bymicrocontroller 26 and communicated by it to the receiver. The latter'sapplication can thus deduce that the vehicle is moving, and that thechild is correctly strapped in.

Thus, while acceleration parameter a=1, the device knows that thevehicle is moving and if, during this period, or journey period, thechild becomes detached, strap 7 will then be in a position close to theone represented in FIG. 3, and the values of the parameters then become:

Gyroscope 22: g=1

Accelerometer 25: a=1

Inclinometer 28: i=0

Sensor device 19: f=0

The matrix of values then becomes equal to [1100] and is obtained bymicrocontroller 26 and communicated to the receiver, which deduces thatthe vehicle is moving but that strap 7 has returned to its initialposition, which implies that the child is detached. The application thensends an urgent alert to the user's receiver, which can be both acousticand visual, similar to “Warning: child unstrapped”.

If only the tightening buckle of the harness becomes detached, sensordevice 19 would then, due to its inherent stiffness, regain an uncurvedshape, and the flexion parameter would adopt value f=0. The values ofthe parameters then become:

Gyroscope 22: g=1

Accelerometer 25: a=1

Inclinometer 28: i=1

Sensor device 19: f=0

The matrix of values becomes equal to [1110] and is obtained bymicrocontroller 26 and communicated to the receiver, which deduces fromit that the vehicle is moving, that strap 7 has indeed remained on theshoulder of the child, but that buckle 5 is unbuckled. The applicationthen sends a message similar to “Warning: child unstrapped.

In an interesting manner, the checking device according to the inventioncan include means enabling the parameters of different child seat modelsto be recorded, in particular in microcontroller 26, and in particularvalue i0 of inclinometer 28 and value f0 of sensor device 19corresponding to the situation represented in FIG. 3, i.e. when the seatis not occupied by a child.

In various variant embodiments of the present invention the reliabilityof the checking device can be improved by using several sensor devicesin a single seat, these sensors being of the same type or of differenttypes.

Thus, as represented in FIG. 19, the checking device according to theinvention includes two sensor devices 19 and 19′, which are installedrespectively in the two retaining straps 7 and 9. These two sensordevices 19 and 19′ each include two accelerometers 24 a and 24 b whichare installed on flexible, elastic tongues 23, 23′. Each of sensors 19,19′ is in remote communication with microcontroller 26, viacommunication means 40, shown by a dotted line in the illustration.Microcontroller 26 can thus easily determine the respective flexionvalues f and f′ of strips 23 and 23′, and therefore those of each ofstraps 7 and 9, from the simple difference of the values delivered bythe two inclinometers. Microcontroller 26 also includes discriminationmeans, of a known type, enabling the redundancy of the flexion valuescommunicated by the two sensor devices 19, 19′ installed on the twostraps 7 and 9 to be processed in the event of conflicting values of thedata communicated by them.

The checking device according to the invention can also include meansenabling account to be taken automatically of the influence of thephysical build of the child, and in particular their size, when they arein position in the seat, and when the retaining strap has been passedover their shoulder, as represented in FIGS. 23a to 23 c.

The device can determine this situation, and therefore record theparameters of the various sensors, and these values can be used asreferences to detect a new situation. Firstly, the angle of inclinationof the strap relative to horizontal is known by means of an inclinometer24 a located at one end of flexible case 18 of the device, and the valueof this angle will vary according to the real or induced physical buildof the child in the seat. Secondly, the curvature of this strap in thearea of the child's shoulder and chest will be known by the value of theangle measured by sensor device 19. These values compared to thereference values stored in a matrix called an “adaptive matrix” enablethe exact way the child is strapped in to be deduced, using appropriatealgorithms.

More specifically, and as represented in FIG. 23a , for a child ofmedian size, rear portion 7 a of strap 7 will be slightly downwardsinclined if headrest 30 of the seat is adjusted upwards and, conversely,it will be slightly upwards inclined if headrest 30 is adjusteddownwards, in order to be roughly horizontal for a headrest adjusted toan intermediate position.

Below we shall consider angle A formed by rear portion 7 a of strap 7with a reference direction, which is given by sensor 24 a, and angle Bformed by front portion 7 b of the latter, with the same referencedirection, which is provided by sensor 24 b. For a child of maximumsize, i.e. the maximum size authorised by the legislation, and for aheadrest 30 adjusted to maximum height, as represented in FIG. 23b ,rear portion 7 a of strap 7 is inclined upwards, and maximum flexionangle B-A of strap 7 is at its greatest possible value.

Conversely, for a small child, and for a headrest 30 adjusted to theminimum height, as represented in FIG. 23c , rear portion 7 a of thestrap is inclined downwards, and flexion angle B-A is at its lowestpossible value.

Under these circumstances it is observed that rear portion 7 a of strap7 is indicative of the height adjustment of headrest 30, and that itsfront portion 7 b is indicative of the child being correctly strappedin. According to the invention, between the two accelerometers 24 a and24 b, as included in the embodiment illustrated in FIGS. 7 to 9, a thirdaccelerometer 24 c (FIG. 21a ) is installed, which will enablemicrocontroller 26 to discriminate between the value of the flexion ofrear portion 7 a of strap 7 due to the adjustment of the headrest withreference to the size of the child with the flexion of the said frontportion 7 b which is indicative of the child being correctly secured.

The checking device according to the invention may also include meanswhich, once the child is correctly strapped into the seat, asrepresented in FIG. 6, enable the values of the inclination and flexionparameters corresponding to this situation to be recorded, and theseparameters will subsequently be used as a reference in the system torecognise whether or not the child is correctly secured in the seat.Actions shall thus proceed as explained above, i.e. by comparing thevalues observed by means of the sensors with the reference valuesrecorded in the adaptive matrix.

FIG. 20 represents a flow chart showing an example operation of achecking device according to the invention.

Microcontroller 26 includes means to put the electronic unit which itcontrols into “sleep mode” when inclinometer 28 and sensor device 19 arenot being used. When the user puts a child 2 in the seat gyroscope 22 isactivated, and it transmits information to a counting loop whichmeasures the amount of data which the gyroscope is sending to it over agiven time, for example two seconds. Such an arrangement enables afiltering system to be created, enabling spurious detections to beeliminated. If this number of data elements is greater than a predefinedvalue, for example 10 in the example represented in FIG. 20,microcontroller 26 calculates the average of the received values, andthis average is then compared to a first threshold value gs, and if itexceeds this threshold value the gyroscope parameter is set at the value1 (g=1), otherwise being set at the value 0 (g=0). This value ofgyroscope parameter g is put into a memory 52 so that it may be combinedwith the values received by the other sensors, in order to form a datamatrix of the following type: [gaif]. Thus, if gyroscope 22 is the onlysensor which reacts the matrix of parameters will be: [1000].

This matrix is sent by microcontroller 26 via Bluetooth communicationmeans 40 to a receiving application loaded, for example, in a smartphone56.

The other sensors, i.e. accelerometer 25, inclinometer 28 and sensordevice 19, include, as represented in FIG. 20, flow chart elements ofthe same type, such that if, in addition to the gyroscope, accelerometer25 reacts and if, as above, the average value of the signals is higherthan a second threshold value as, then acceleration parameter a becomesequal to 1 and the matrix of parameters becomes equal to: [1100].

Similar reasoning applies for inclinometer parameter i supplied byinclinometer 28 and for parameter f supplied by sensor device 19.

We shall consider below, as examples, the main situations which mayoccur during a process starting from the situation of a seat at restuntil, once again, the seat returns to its “rest” state after thevehicle has accomplished a journey with the child.

Matrix of Situation parameters Message Seat at rest: 0000 Child in theseat: 1000 Child in the seat Strap passed over the 1010 Child notstrapped in shoulder: Harness tightened: 1011 Child correctly strappedin Vehicle moving and strap 1110 ALERT: CHILD UNSTRAPPED unbuckled:Vehicle stopped, child 1000 Child detached detached Child has left theseat 0000

According to the invention, the remote receiver may, in addition tosmartphone 56 mentioned above, consist of an object in the user'spossession, and could for example consist of a key fob belonging tothem.

In a simplified embodiment of the invention, microcontroller 26 will notbe in communication with a remote receiver such as a smartphone, butwill be able to transmit by itself the data for the user's attention, inparticular by acoustic means. These warnings may consist of sounds ofdifferent kinds generated by one or more buzzers, or of voice messagesemitted by a voice synthesiser associated with microcontroller 26.

In a variant of the present invention, a vibrator may be added to thedevice which, in an educational and preventative aim, will firstly alertthe child, reminding them that they must not unstrap themselves whenthey are installed in their seat and when the vehicle is moving.

A presence sensor, for example a capacitive sensor, and in particular asensor using the variation of capacitance of a loop which detects when abody having mass is brought within proximity of it, can be added to thedevice, to introduce redundancy into the sensors, such that the devicemeets the motor vehicle standard which requires that a defective sensorenables the system to continue to operate without danger. To this end,and as represented in FIG. 21a , sensor device 19 can include acapacitive antenna 54 which extends, for example, in the direction ofthe length of flexible tongue 23, and which enables microcontroller 26to detect, possibly redundantly with gyroscope 22, the presence of achild in seat 1.

In a variant, and as represented in FIG. 21b , three capacitive antennae54 a, 54 b, 54 c, connected to microcontroller 26, have been installedon flexible tongue 23. These capacitive antennae, which may be installedbetween accelerometers 24 a and 24 b, enable microcontroller 26 toobtain a measurement of a capacitance relating to the presence of waterin the body of the child through the latter's clothing, which isrepresentative of the distance between this sensor and the child's body.Thus, if the child is correctly strapped in, case 18 containing sensordevice 19 is located almost parallel to the child's body in thislocation, such that the capacitive measurements provided by the threecapacitive antennae 54 a, 54 b and 54 c will be close to one another,independently of the other implied factors such as, in particular, thethickness of the child's clothing, or whether they are dressed lightlyin a T-shirt or in a thick cloak. If this is not the casemicrocontroller 26 will have data in addition to that of the othersensors, indicating that the way the child is strapped in, and thereforethe way they are secured, are not correct.

According to the invention the application controlling microcontroller26 may include a self-test program which will be run each time the carseat is used, in particular after a prolonged stop.

In a variant of the present invention the inclinometer will consist ofthe accelerometer itself, which will thus be able to provide, firstly,the actual acceleration of the vehicle, in three axes xx′, yy′, zz′, andalso the inclination of case 18 containing electronic circuit 20 andsensor device 19. This being so, the flow chart relating toaccelerometer 25 and to inclinometer 28 is replaced by the onerepresented in FIG. 22.

Of course, and as mentioned above, the signal processing means mayinclude electronic elements able to transmit the alarm signal remotely,for example via a Bluetooth link 40 to smartphone 56 of the user, bymeans of a dedicated application of this smartphone. The means forprocessing the signal could also transmit the alarm signal to an objectbelonging to the user, in particular by means of a link of the radiofrequency type. They could also transmit the alarm signal to receiverelements which are securely attached to the motor vehicle's dashboard.

The present invention is particularly interesting in that the presentchecking device can be installed on any seat, whatever its type ortrademark, with no requirement, unlike the devices of the prior state ofthe art, to accomplish any technical adaptation whatsoever on the seat.

This being the case, manufacturers of child seats can thus install thechecking device on the various models of their range of existing seatswithout modification, and users can also use the checking device onvarious seats owned by them, without modification.

The system according to the invention proves to be particularly easy toinstall, since to use it one need merely attach it to the upper portionof one of the straps, i.e. in an area close to that area where the saidstrap passes through the back of the seat.

Although the checking device according to the present invention provesto be particularly interesting when checking the satisfactoryoperational and tension condition of a child's car seat harness, itcould also be used in other fields where it is necessary to hold anoccupant in a seat under correct safety conditions.

Such a seat could, of course, be a seat intended for an adult, and couldconsist not only of a car seat, but also of a seat of the type used inother means of locomotion, and in particular in the aviation field.

The strap holding an occupant in a seat could also be something otherthan a shoulder strap, and could in particular be a lap belt.

The invention claimed is:
 1. A device for checking that a securingharness, for a safety seat, including at least one retaining strapsubjected to tension when the harness is in the state of holding anoccupant, is in a correct operational condition, wherein said device isconfigured to be installed in a determined area of the strap, the devicecomprising: at least one sensor device including an elongated, flexibleelement which is positionable on said strap in said determined area,which has measuring means able to measure, in said determined area, atleast one level of flexion and/or inclination of said strap, means ableto obtain values relating to the level of flexion and/or inclination,internal or external means able to analyse the values and to communicateto receiver means data concerning the operational condition of saidsecuring harness.
 2. The checking device according to claim 1, whereinthe retaining strap is a shoulder strap.
 3. The checking deviceaccording to claim 2, wherein said determined area is close to alocation where it is intended for the strap to be pressing against theshoulder of the occupant.
 4. The checking device according to claim 1,wherein the sensor device is associated with an electronic circuit, andthe elongated, flexible element is attached to it, both of theseelements being contained in a flexible, elastic envelope so as to form amodule which can be immobilised relative to the strap.
 5. The checkingdevice according to claim 4, wherein one end of the device includesmeans able to attach it, to a headrest of the child seat.
 6. Thechecking device according to claim 4, wherein the flexible envelope haselasticity such that, when the flexible envelope is under no stress, theflexible envelope has an unbent shape.
 7. The checking device accordingto claim 6, wherein the elasticity of the flexible envelope iscommunicated to it, at least partly, by an additional spring element. 8.The checking device according to claim 7, wherein the additional springelement consists of at least one snap ring made of synthetic fibre. 9.The checking device according to claim 1, further comprising electronicmanagement means containing a program to control the various sensors.10. The checking device according to claim 1, further comprising meansfor remote communication with receiver means.
 11. The checking deviceaccording to claim 1, further comprising one or more sensors configuredto output data based on the physical characteristics of the occupant.12. A sensor device configured to implement a checking device forchecking that a securing harness, for a safety seat, including at leastone retaining strap subjected to tension when the harness is in thestate of holding an occupant, is in a correct operational condition,said checking device configured to be installed in a determined area ofthe strap, the checking device comprising said sensor device, means ableto obtain values relating to a level of flexion and/or inclination ofthe strap, and internal or external means able to analyse the values andto communicate to receiver means data concerning the operationalcondition of said securing harness, the sensor device comprising anelongated, flexible element which is positionable on said strap in saiddetermined area, which has measuring means able to measure, in saiddetermined area, said level of flexion and/or inclination of said strap.13. The sensor device according to claim 12, wherein the sensor deviceis integrated in the retaining strap.
 14. The sensor device according toclaim 12, wherein said measuring means include at least one inclinationsensor.
 15. The sensor device according to claim 14, wherein the atleast one inclination sensor consists of an accelerometer.
 16. Thesensor device according to claim 12, wherein the sensor device includestwo inclinometers installed roughly at respective ends of the elongated,flexible element, wherein a difference between the two values deliveredby the two inclinometers gives a value of the level of flexion of thestrap.
 17. The sensor device according to claim 16, wherein at least oneother inclinometer is installed between the two inclinometers.
 18. Thesensor device according to claim 12, wherein the elongated, flexibleelement includes, at one end, a target in which one area becomesseparated from a reference area when it is subjected to flexion, andwherein measuring means are installed to measure the distance betweenthe target and said reference area.
 19. The sensor device according toclaim 18, wherein the flexible element is formed from an elongatedsheath, an upper wall and lower wall of which are kept apart byseparating elements, with the target installed in a portion of thesheath distant from the strap.
 20. The sensor device according to claim18, wherein the measuring means include a laser diode device.
 21. Thesensor device according to claim 19, further comprising two electrodesinstalled on the target and in the reference area which constitute acapacitance with the air which separates them as a dielectric, and alsomeans for measuring the value of the capacitance.
 22. The sensor deviceaccording to claim 12, wherein the flexible, elongated element iscovered with a coating, such that its electrical resistance varies whenit is bent.
 23. The sensor device according to claim 22, wherein theelongated, flexible element is covered with a coating containingembedded conducting particles which, when it is appreciably rectilinear,give it a given resistance and, when it is curved, a resistance ofanother value.
 24. The sensor device according to claim 22, furthercomprising means to measure the value of said resistance.
 25. The sensordevice according to claim 12, wherein the elongated, flexible elementincludes at least one capacitive sensor.
 26. A safety seat comprising achecking device according to claim 1.